In certain types of security seals, a stranded cable is used as a shackle. The ends of the cable are inserted into spaced apertures in a housing which has internal means for allowing the cable to enter said apretures freely, but prevent reverse movement, said means often being a wheel or disc which, on reverse movement of the cable, is pulled into a narrower portion of the aperture, jamming the cable against further movement.
It has been found that such seals can often be defeated by twisting the cable, so that the grooves between the cable strands act as threads, allowing the cable to back out of the housing.